Film transport for a motion picture camera

ABSTRACT

Film transport for a motion picture camera with a claw 2, of which at least one claw tip 21, 22 advances the film to be transported, provided with perforations on one edge 10, stepwise past a gate, and a transport drive which comprises a working arm 5 connected with the middle segment 20 of claw 2 with articulation, said arm being connected by a claw crank pivot 12 with a crank arm 4 and moving claw 2 in such fashion that claw tips 21, 22 traverse an elongated closed curve which at one end enters the film plane and at the other end leaves it again, with crank arm 4 being coupled by a control arm 6 with a fixed bearing 14 of an oscillation crank 7, said crank being connected end segment 23 of claw 2 with articulation.

The invention relates to a film transport mechanism for a motion picturecamera.

DE-PS 36 43 594 teaches a film transport mechanism in a motion picturecamera that moves the film, perforated along both edges, to betransported stepwise past a gate with the aid of transport claws insteps, said claws, together with the corresponding transport drive,being located on both sides of and symmetrically with respect to thecentral plane running vertically along the center of the film. Thetransport claws are moved by the respective transport drives in suchmanner that the tips of the claws traverse an elongated, closed curvewhich enters the film travel plane at one end and leaves it again at theother end.

For this purpose, each transport drive has two shafts, each coupled witha crank. The end of one crank forms a pivot at which the transport clawstrap is articulated. In the middle portion of the transport claw strapthere is likewise a pivot at which a connecting rod is articulated, saidrod being connected with the end of the other crank. The two shaftsconnected with the cranks are connected by a rotating toothed pulleywith a main drive shaft with the transport drives opposite one anotherbeing driven by the same common drive shaft which is mounted in onebearing on either side of the central plane.

In addition, a crank drive for a locking claw is provided, said drivebeing connected with the shaft driving the end of the transport clawstrap. The angular displacement between the two cranks on the commonshaft is selected so that the locking claw is outside the film planewhen the transport claw tips are advancing the film.

One disadvantage of the known film transport mechanism consists in thefact that in order to change the advancing step and the angularrelationships, in other words, the depth of penetration and path of thetips of transport claw, considerable design modifications are requiredand the length of the stroke is relatively large so that the film, as aresult of engagement of the transport claw tips in the perforationholes, is moved along a curved path which results in a so-called "sawingaction" produced by the sliding of the transport claw tips in the filmperforations.

A claw transport is known from DE-PS 385 819, said transport consistingof two cranks, of which the first crank acts on one end of a rod withthe claw pins, while the second crank is connected by an intermediatelever with the other end of the rod. Both cranks are coupled together bygears. In this known claw transport, considerable design modificationsare required to change the depth of penetration and the path of movementof the claw tips in order to achieve a depth of penetration of the clawtips which is as small as possible yet sufficient depending on the localconditions.

The goal of the present invention is to improve a film transportaccording to the species in terms of its adaptability to localconditions.

The solution according to the invention provides a film transportmechanism which can be adapted simply to local conditions so that, withminor changes, different stepping and pulling angle relationships and adifferent stroke length are made possible and easy balancing of thetransport is ensured, with limited space requirements in the vicinity ofthe film path being achieved as well.

The improved adaptability of the film transport mechanism to localconditions results in an extremely high resistance to wear and a lownoise level of the film transport, making possible different step andangle relationships with minor conversion measures and avoidingbalancing problems. In addition, a working curve for the claw isachieved which can be changed with minor technical means, the tips ofsaid claw penetrating shallowly yet sufficiently into the filmperforations and, at the end of the stroke, being pulled in the shortestpossible time nearly perpendicularly out of the film perforations.

The film transport mechanism, limited mechanical means, permitsdifferent step and angle relationships, for example, advancing two,three, four, five, or six holes at a time and, optionally, a one-sidedor two-sided drive, in which two film transports engage two rows ofperforations in a film and transport said film.

This produces a film transport mechanism which is easy to adjust, inwhich only minor changes are required for adjustment to localconditions, whereby previously new claw systems had to be developed andbuilt constantly. In the present film transport mechanism, by simplyexchanging individual elements of the film transport mechanism, themagnitude of the stroke and the depth of penetration of the claw can bechanged so that transport steps of different sizes can be implementedand the path of movement of the claw tips can be varied nearly at will.

One advantageous embodiment of the solution according to the inventionis characterized by the fact that the control arm slides along a controlcurve by its end opposite the pivot. By using a control curve, there aremore design possibilities for the movement of the claw so that nearlyany path of movement of the claw tips is possible. However, onedisadvantage of this arrangement is that the noise is greater.

Another embodiment of the solution according to the invention ischaracterized by the fact that the claw lever is extended beyond thefixed bearing and there is a pivot bearing at its end, said pivotbearing moving a locking claw pin, mounted perpendicularly to the filmplane, back and forth by means of a claw lever and an additional pivotbearing.

Connecting the locking claw to the claw lever ensures that without anydesign changes in the control for the locking claw, its motion can becoordinated with the motion of the claw so that a change in thekinematics of the claw automatically results in a change in the movementof the locking claw.

Advantageous improvements on the invention will be described in greaterdetail below together with the description of the preferred embodimentof the invention with reference to the figures.

FIG. 1 is a schematic view of the individual elements of the filmtransport mechanism according to the invention;

FIG. 2 is a view according to FIG. 1 explaining the variation of thedimensions of the individual elements in the film transport mechanism;

FIG. 3 is a side view, partially in cross section, of the film transportmechanism;

FIGS. 4 to 6 show various views of the transport axis structure;

FIG. 7 is a graphic representation of the working curve of the claw;

FIG. 8 is a detailed view of the claw tips;

FIG. 9 is a sequence showing the engagement of the claw tips in theperforation holes of a film; and

FIG. 10 is a top view of the locking claw tip.

FIGS. 1 to 3 show schematically and in partially sectioned side viewsthe construction of the film transport mechanism according to theinvention for a motion picture camera for transporting a film 1.

The film transport mechanism has a claw 2 provided at one end with clawtips 21, 22, said tips engaging perforation holes 10 in film 1. Themiddle section 20 of claw 2 has a claw strap point 13 at which one endof a working arm 5 of a claw crank is articulated, the other end of saidarm being connected with a claw crank pivot 12.

Claw crank pivot 12 is part of a working arm 8 which, together with acrank arm 4, is connected with a transport mechanism axis 9. Drive shaft11 is connected by a coupling part with a drive motor, not shown ingreater detail.

Crank arm 4 has a control crank pivot 19, to which one end of controlarm 6 is articulated. Drive shaft 11, crank arm 4, and drive arm 8 areparts of transport axis structure 9 which additionally has a balancingsegment 40 (FIGS. 4-6) which makes possible a dynamic balancing of thedrive parts of the film transport mechanism in simple fashion.

The other end of control arm 6 is connected by a pivot 15 with anoscillating arm 71, which forms one lever of an oscillating crank 7.Oscillating crank 7 is mounted in a fixed bearing 14 and has a secondlever in the form of a claw lever 72 as well as an extension 73, withthe three levers 71, 72, 73 of oscillating crank 7 being in a fixedgeometric relationship to one another.

The end of claw lever 72 forms a claw pivot 16, to which the end 23 ofclaw 2 which is opposite claw tips 21, 22 is articulated.

Extension 73 is connected with a pivot bearing 17 to which a lockingclaw lever 31 is articulated. Locking claw lever 31 is connected by apivot bearing 18 with a locking claw strap 32, shrunk onto a lockingclaw pin 3, the leading flattened tip of said pin engaging perforationholes 10 in film 3 to hold the frame in place.

FIG. 3 shows in solid lines the beginning of the stroke of claw 2 aswell as locking claw pin 3, which is disengaged from perforation holes10 in film 1, while the dashed lines show the end of the stroke of claw2 as well as locking claw pin 3, which is engaged in perforation holes10. The transport direction of the film therefore runs in the directionof arrow A, while the claw stroke is shown by H in FIG. 1.

FIG. 2 shows the lever lengths and principal dimensions of the filmtransport mechanism in a schematic diagram.

Similarly to the representation in FIG. 1, drive shaft 11, control crankpivot 19, on which control arm 6 is articulated, claw crank pivot 12, onwhich working arm 5 is articulated, and claw strap point 13, to whichworking arm 5 is connected with middle section 20 of claw 2, lie on aline.

As shown in the drawing in FIG. 2, the claw passes through an angle ofabout 21° around the center of the stroke as it moves back and forth. Toexecute the stroke movement of the claw, control arm 6 executes alimited stroke, while, for example, as a consequence of the length ofthe leg of extension 73 of oscillating crank 7, a greater stroke isexecuted in the vicinity of pivot bearing 17, resulting in acorrespondingly deep penetration of locking claw pin 3 into theperforation holes 10 of film 1.

One important advantage of the solution according to the inventionconsists in the fact that, on the one hand, by provision of a controlarm 6, a limited stroke of this control arm 6 is sufficient to cause alarge stroke of locking claw pin 3 and, on the other hand, as a resultof minor change in the dimensions of the individual film transportelements or by a displacement of the pivot points, the depth ofpenetration and the stroke can be influenced. This simple influence onstroke and depth of penetration of the tips of locking claw pin 3 aswell as claw tips 21, 22 is especially advantageous for equippingvarious motion picture cameras, since the individual requirements can betaken into account with simple means.

Thus, the film transport mechanism according to the invention can beeasily converted to advance the film one, two, three, four, or fiveholes at a time, without a special film transport mechanism having to bedesigned for the purpose. Likewise, a straight or curved film path canbe produced by setting the depth of penetration of the claw tipsappropriately.

In addition, one-sided or two-sided mounting of the film transport forone-sided or two-sided transport of a film is possible. On importantadvantage of the solution according to the invention also consists inthe fact that, by suitably displacing the film transport parts away fromthe film plane, sufficient space is created in the vicinity of the filmplane to dispose there the additional elements of a motion picturecamera.

According to FIG. 2, a uniform change in the length of stroke H can beachieved by changing the length a of drive arm 8. A unilateral change inthe length of the stroke in the upper area of the stroke can be producedby changing dimension b of claw lever 72.

A unilateral change in the length of the stroke in the lower area isaccomplished by changing dimension c of claw 2 between claw pivot 16 andclaw strap point 13, as well as by shifting the center of the axis ofoscillation crank 7 in the direction of the claw corresponding to arrowA.

The length of the stroke can be changed by varying dimension d ofworking arm 5.

All pivot points 12 to 19 in the film transport mechanism can optionallyconsist of ball bearings or sleeve bearings, whereby the former permitzero maintenance operation of the film transport mechanism while thelatter provide an even lower noise level during operation, but requireoccasional maintenance especially in motion picture cameras with hightransport speeds.

Another opportunity consists in using roller bearings characterized onthe one hand by zero maintenance and on the other hand by loweroperating noise than ball bearings. Therefore, depending on theapplication and purpose of the motion picture camera, suitable bearingsfor the pivot points can be provided, with no design changes in the filmtransport being required.

The side view in FIG. 3 of the film transport mechanism shows thegeometric configuration of the individual transport elements and makesespecially clear the construction of transport axis structure 9,oscillation crank 7, and claw 2.

Transport axis structure 9 carries claw crank pivot 12 as well ascontrol crank pivot 19, to which working arm 5 and control arm 6 arearticulated. In addition, transport axis structure 9 has a balancingsegment 40 which serves for dynamic balancing of the film transportmechanism.

Oscillation crank 7 consists of claw lever 72 and extension 73 whichform an obtuse angle between them, to which oscillating arm 71 isarticulated in a fixed angular relationship. Oscillating crank 7oscillates around fixed bearing 14, driven by control arm 6.

While the film is in the gate, locking claw pin 3 engages a perforationhole 10 in film 1 by its tip and during film transport is disengagedfrom perforation holes 10 in film 1. By rotating locking claw pin 3through 180°, locking claw pin 3 can be simply adjusted.

FIG. 4 shows a bottom view and FIG. 5 a side view and FIG. 6 a rear viewof transport axis structure 9.

Transport axis structure 9 comprises drive shaft 11 connected with adrive motor, crank arm 4 with control crank pivot 19 for articulatingcontrol arm 6, balancing segment 40, and drive arm 8 with claw crankpivot 12 to articulate working arm 5. The transport axis structure isbalanced by changing balancing segment 40, since both crank arm 4 anddrive arm 8 are located on the same side of transport axis 9, so thatdynamic balancing can be accomplished in simple fashion.

FIG. 7 is a schematic diagram of the working curve of the transport clawrelative to film plane 100 and shows the extremely shallow depth ofpenetration of the claw tips into the film perforations, so that,firstly, excessive stress on the film perforations is avoided and,secondly, the flat film path is not adversely affected.

The degrees entered in the schematic diagram of the claw working curvein FIG. 7 refer to the angle of rotation of crank arm 4, with the startof the stroke being set at 0° or 360°. The diagram in FIG. 7 is intendedto show that crank arm 4 has passed through an angle of rotation of 120°from the start of the stroke to the end of the stroke, whereby thisportion of the curve of the engagement of claw tips in the filmperforations is characterized by a flat uniform path.

During the backward movement of the claw, the claw tips execute amovement shown to the left of the film plane, which extends over anangle of rotation from 120° to 360° of crank arm 4.

FIG. 8 shows, enlarged, the shape of claw tips 21, 22, which are sodesigned that, firstly, gentle engagement in the film perforations isproduced by alternate contact of the claw tips with the respectiveperforation edges in the film and, secondly, the film, during themovement of claw 2 during its stroke, can slide along claw tips 21, 22and is therefore not forced to follow the limited stroke movement ofclaw 2.

Claw tip 21, which is forward in the direction of transport of the film,has a flattened leading edge 210 which is beveled at the top edge 211 inthe direction of transport of the film.

Claw tip 22, which is at the rear in the direction of transport, on theother hand, has a sloping leading edge 220 which likewise is beveled atthe top edge 221 in the direction of transport of the film.

FIG. 9 illustrates the individual phases of movement of the claw tipsupon engagement with the film perforations, whereby six stroke phasesbeginning with 0° and 360°, 30°, 56°, 83°, 100°, and 120° are shown.

At the start of the stroke (0° or 360°), the film is advancedexclusively as a result of claw tip 21, which is forward in thedirection of transport, while claw tip 22, which is at the rear in thedirection of transport of the film, engages the following perforationhole with play. With an angle of rotation of 30°, both claw tips 21 and22 contribute the same degree of pull, since the leading edges of bothclaw tips 21 and 22 abut the leading edges of the successive perforationholes in the film. The same applies at the middle of the stroke, reachedat about 56°.

With an angle of 83°, equal pull by claw tips 21, 22 is likewiseensured.

At an angle of 100°, only the leading edge of the rear claw tip 22 abutsthe leading edge of the respective perforation hole, while claw tip 21,which is forward in the direction of transport of the film, is nowdisengaged from the respective hole.

At the end of the stroke (120°) only the beveled leading edge 221 ofclaw tip 22, which is at the rear in the direction of transport of thefilm, abuts the leading edge of the respective perforation hole in thefilm.

FIG. 9 shows that the special shape of the claw tips in combination witha limited depth of penetration of the claw tips into the filmperforations ensures that the perforation holes slide along the clawtips during the stroke, so that the film is essentially held in the filmplane and does not follow a curve.

To control control arm 6, instead of a crank arm 4, a curve control, forexample, a cam disk, can be provided, with influence on the movement ofthe claw to influence the end points of the curve according to FIG. 7 ismade possible. As a result, for example, the insertion movement causedby the control arm can be suspended at the end points, so that nearlyany paths of movement of the claw tips can be achieved. In this manner,for example, straight and circular film paths are possible with the filmtransport according to the invention.

FIG. 10 shows a top view of the tip of locking claw pin 3 whoseadjusting surfaces 35 and 36 are staggered with respect to the center oflocking claw pin 3 by a small amount so that, by rotating locking clawpin 3 through 180°, a different point of engagement of locking claw pin3 is achieved. Adjusting surfaces 35 and 36 have a beveled areaindicated by dashes to facilitate engagement of locking claw pin 3 inperforation holes 10 of film 1.

I claim:
 1. A motion picture camera film transport mechanism fortransport of perforated film along a film plane past gate structurecomprisingdrive structure mounted for rotation about a fixed axis,oscillating structure mounted for oscillation about a bearing spacedfrom said fixed axis, claw arm structure for engaging a film perforationto advance the film stepwise through said gate structure of the motionpicture camera said claw arm structure having a claw tip at one end anda claw pivot at its other end, a working arm coupled between said drivestructure and said claw arm structure at a point intermediate said clawtip and said claw pivot for reciprocating said claw tip along a closedcurved path to cause said claw tip to penetrate the film plane at oneend of said path and leave it again at the other end of said path, saidoscillating arm structure including first and second arm members, saidclaw pivot of said claw arm connected by said first arm member of saidoscillating arm structure in articulated fashion, and control armstructure pivotally coupled at one end to said drive structure and atthe other end to said second arm member of said oscillating armstructure.
 2. Film transport mechanism of claim 1 and further includinglocking claw structure, and wherein said oscillating arm structureincludes three arm members permanently connected to one another forpivoting movement about said bearing, and the third arm member iscoupled to said locking claw structure for moving said locking clawstructure perpendicularly to said film plane in back and forth motion.3. Film transport mechanism of either claim 1 or 2 where said controlarm structure is coupled to said drive structure for sliding movementalong a control curve.
 4. Film transport mechanism of either claim 1 or2 and further including adjustment structure for adjusting the positionof said bearing and the effective length of said working arm.
 5. Filmtransport mechanism of either claim 1 or 2 wherein said drive shaftstructure includes a balancing segment located between said claw pivotand said control arm pivot.
 6. Film transport mechanism of either claim1 or 2 wherein said bearings and pivots of said transport mechanism areball bearings.
 7. Film transport mechanism of either claim 1 or 2wherein said claw arm has first and second claw tips locatedsequentially in the film transport direction, the leading edge of eachsaid tip in the direction of film transport being beveled in suchfashion that during each transport step, initially the leading edge ofsaid first claw tip and then the leading edge of said second claw tipengages respective perforation edges of the film, and said leading edgeof said first claw tip comes free of its corresponding perforation edgeas soon as said leading edge of said second claw tip comes in contactwith the perforation edge engaged by said second claw tip.
 8. A motionpicture camera film transport mechanism for transport of perforated filmalong a film plane past gate structure comprisingdrive structure mountedfor rotation about a fixed axis, oscillating structure mounted foroscillation about a bearing spaced from said fixed axis, saidoscillating arm structure including first, second and third arm memberspermanently connected to one another for pivoting movement about saidbearing, locking claw structure, claw arm structure for engaging a filmperforation to advance the film stepwise through said gate structure ofthe motion picture camera said claw arm structure having a claw tip atone end and a claw pivot at its other end, a working arm coupled betweensaid drive structure and said claw arm structure at a point intermediatesaid claw tip and said claw pivot for reciprocating said claw tip alonga closed curved path to cause said claw tip to penetrate the film planeat one end of said path and leave it again at the other end of saidpath, said claw pivot of said claw arm connected by said first armmember of said oscillating arm structure in articulated fashion, andcontrol arm structure pivotally coupled at one end to said drivestructure for sliding movement along a control curve and at the otherend to said second arm member of said oscillating arm structure, thethird arm member coupled to said locking claw structure for moving saidlocking claw structure perpendicularly to said film plane in back andforth motion.
 9. Film transport mechanism of claim 8 and furtherincluding adjustment structure for adjusting the position of saidbearing and the effective length of said working arm.
 10. A motionpicture camera film transport mechanism for transport of perforated filmalong a film plane past gate structure comprisingdrive structure mountedfor rotation about a fixed axis, oscillating structure mounted foroscillation about a bearing spaced from said fixed axis, saidoscillating arm structure including first, second and third arm memberspermanently connected to one another for pivoting movement about saidbearing, locking claw structure, claw arm structure for engaging a filmperforation to advance the film stepwise through said gate structure ofthe motion picture camera said claw arm structure having a claw tip atone end and a claw pivot at its other end, a working arm coupled betweensaid drive structure and said claw arm structure at a point intermediatesaid claw tip and said claw pivot for reciprocating said claw tip alonga closed curved path to cause said claw tip to penetrate the film planeat one end of said path and leave it again at the other end of saidpath, said claw pivot of said claw arm connected by said first armmember of said oscillating arm structure in articulated fashion, controlarm structure pivotally coupled at one end to said drive structure andat the other end to said second arm member of said oscillating armstructure, the third arm member coupled to said locking claw structurefor moving said locking claw structure perpendicularly to said filmplane in back and forth motion, and adjustment structure for adjustingthe position of said bearing and the effective length of said workingarm.
 11. Film transport mechanism of either claim 8 or 10 wherein saiddrive shaft structure includes a balancing segment located between saidclaw pivot and said control arm pivot.
 12. Film transport mechanism ofeither claim 8 or 10 wherein said bearings and pivots of said transportmechanism are ball bearings.
 13. Film transport mechanism of eitherclaim 8 or 10 wherein said claw arm has first and second claw tipslocated sequentially in the film transport direction, the leading edgeof each said tip in the direction of film transport being beveled insuch fashion that during each transport step, initially the leading edgeof said first claw tip and then the leading edge of said second claw tipengages respective perforation edges of the film, and said leading edgeof said first claw tip comes free of its corresponding perforation edgeas soon as said leading edge of said second claw tip comes in contactwith the perforation edge engaged by said second claw tip.